CVE-2026-59944: Composer: GHSA-gjfg-22fp-rrxx fix bypass via symlinked package bin path

A malicious or compromised Composer package could, when installed as a dependency, cause Composer to change the permissions of a file outside that package’s own directory and to register a runnable vendor/bin command that points at that outside file. This is a path traversal and link following issue. It is not remote code execution, the attacker gains no ability to read or receive your data directly. The risk is that a file which was readable only by its owner, but modifiable by Composer, can be made world readable and executable, which is enough to expose its contents on a shared or multi tenant host. The earlier hardening from GHSA-gjfg-22fp-rrxx can be bypassed, since it only rejected literal .. path segments in a package’s declared binaries, and was only applied in a single place during dependency resolution.